Why Reverse Osmosis and Nanofiltration Are Ideal for Water Recycling Systems?

In the wastewater recycling process, the choice of the filtration system plays a paramount role in maintaining the resultant water quality and ensuring sustainability in the environment. Nanofiltration and Reverse Osmosis are two widespread technologies that are used for water filtration in wastewater treatment systems. Both of these technologies offer various advantages and have applications curated for specific water treatment needs. Leveraging nanofiltration and reverse osmosis in wastewater treatment gives you tremendous benefits in getting high-quality water. Let’s understand in detail.

What are Reverse Osmosis and Nanofiltration?

Reverse Osmosis:

In the reverse osmosis technology, high pressure is used to force water through a reverse osmosis membrane to yield pure water. A high-pressure pump is used in the process, which applies pressure higher than osmotic pressure on the water (generally about 4 MPa). The pre-treated water has to pass through the semi-permeable membrane in the opposite direction of natural osmosis.

The size of the pores in the reverse osmosis membrane is quite small, with an accuracy of up to 0.0001 microns. Thus, reverse osmosis technology can remove 99% of impurities like dissolved salts, heavy metals, microorganisms, suspended articles, and other impurities from water. The selective permeability of the semi-permeable membrane used in reverse osmosis allows only water molecules to pass through. The impurities present in the wastewater get trapped on the other side of the membrane and are highly concentrated in wastewater. You get high-quality water on the other side.

Application of Reverse Osmosis:

There are various applications of reverse osmosis, such as:

1. Desalination:

Reverse Osmosis is highly used in seawater and brackish water desalination plants to produce fresh water suitable for drinking, agriculture, and industrial processes.

2. Purification of Drinking Water:

RO is a common system used for the purification of drinking water in households, businesses, and municipal water treatment plants. It can remove dissolved solids, contaminants, and microorganisms and ensure safe plus high-quality water.

3. Boiler Feedwater Treatment:

Boiler Feedwater Treatment is important in the industrial processes in which RO serves as an essential step. It helps in preventing scale formation and corrosion in boilers and other equipment.

4. Wastewater Reuse:

RO is utilized in wastewater treatment plants to produce high-quality effluent, which can be further reused in various industrial processes, irrigation, and other purposes.

Nanofiltration:

The working procedure of nanofiltration is quite similar to that of the RO system, in which external pressure is required, along with the use of semi-permeable membranes for selective permeation. The system leverages the charge adsorption and selective permeation characteristics of nanofiltration membranes for pollutant removal. The filtration accuracy of nanofiltration membranes is 0.001 microns, and the pressure required for this process is lower than that of the RO process. It usually lies between 0.5 and 2.5 MPa.

Nanofiltration technology can remove some of the substances that reverse osmosis can remove. However, the difference is that a small amount of divalent ions (such as calcium and magnesium) and monovalent ions (such as sodium and potassium) will pass through the semi-permeable membrane along with the water molecules. Thus, the nanofiltration-treated water contains some traces of elements and minerals.

Applications of Nanofiltration:

1. Water Softening:

Nanofiltration is highly used in water-softening applications. It is highly efficient in removing salts of calcium, magnesium, and other hardness ions to improve water quality for industrial as well as domestic use.

2. Color and Odor Removal:

In the wastewater treatment process in municipal treatment, nanofiltration is mostly used for the removal of color, odor, and taste-causing compounds, improving the aesthetic quality of the water.

3. Wastewater Reclamation:

It is essential for treating industrial wastewater and secondary effluent so that they can be used again in non-potable applications such as cooling water, industrial operations, and irrigation.

4. Selective Ion Removal:

Because NF membranes can remove particular ions selectively, they are useful for regulating water quality and process efficiency in sectors including electronics, food & beverage, and pharmaceuticals.

How Reverse Osmosis and Nanofiltration are Similar?

In both of these technologies, high external pressure is applied to the wastewater stream, driving it through a semi-permeable membrane for dissolved solids removal. In this manner, RO and NF have a close semblance of membrane filtration. Both these technologies are capable of removing the smallest molecules, such as dissolved organics, pesticides, heavy metals, and other impurities.

Both Benefit from Pretreatment:

The function of reverse osmosis and nanofiltration is to remove smaller particles from the wastewater. Thus, they can foul quickly if larger particles aren’t removed by upstream filtration technologies like media filtration. There can be problematic particulates present in the wastewater, which require pretreatment. It also helps reduce the amount of energy required to maintain adequate pressure in an RO/NF system.

Both Require Pressure for Optimal Functioning:

Both RO and NF require energy to move water over their membranes despite being reasonably effective purification methods. This is because the retentate side of the membrane has a high concentration of salts and other substances due to their tiny holes. That’s why enough pressure must be applied so that the wastewater stream can overcome the osmotic pressure that causes water to resist flowing through the membrane.

How Reverse Osmosis and Nanofiltration are Different?

Despite their striking similarities, RO and NF can be differentiated by the size of the particles they can remove. Hardness, nitrates, sulfates, total dissolved solids (TDS), heavy metals, radionuclides, and organic macromolecules can all be eliminated from process and waste streams using RO and NF. These technologies can remove finer contaminants than microfiltration and ultrafiltration.

In terms of pore size, RO is the finest of all membrane systems. Its extremely small pores are capable of removing particles as small as 0.1nm. On the other side, nanofiltration is slightly coarser filtration than RO, and it can remove particles as small as 0.002 to 0.005 μm in diameter.

How can Wipro Water Help?

Our experts have vast experience in custom designing and installing reverse osmosis and nanofiltration systems for industrial wastewater treatment systems. We provide tailored solutions for wastewater treatment plants.

We pride ourselves in delivering cutting-edge technologies and unparalleled expertise to optimize your water treatment processes. Let us know your requirements.